Passive devices perform important functions in an electronic system. Recently, making miniaturized, multi-functional, and economical electronic appliances has given rise to requirements for passive devices to be fabricated in the form of an array, a network, and a built-in passive device. Such passive devices sense, monitor, transmit, reduce, and control voltage.
Resistors as passive devices may suppress a flow of electric charge current, thereby controlling the amount of current. Such passive devices may be classified as a thin film resistor, in which a metal layer is thinly deposited to form a pattern, and an active layer resistor using an active layer area. Among these, the thin film resistor is generally positioned between metal lines of a semiconductor device.
FIGS. 1 and 2 are sectional views of a semiconductor device including a thin film resistor pattern according to the related art. Referring to FIG. 1, a semiconductor device includes a first insulation layer 21 disposed on a semiconductor substrate 10, lower metal lines 30 and 31 disposed on the first insulation layer 21, and a thin film resistor pattern 40 connecting the lower metal lines 30 and 31 to each other. FIG. 1 illustrates a simple process in which the thin film resistor pattern 40 is directly formed after the lower metal lines 30 and are formed. However, the thin film resistor pattern 40 is generally formed using a sputtering process. Thus, it is difficult to uniformly form the thin film resistor pattern 40 on edge portions of the lower metal lines 30 and 31 because the thin film resistor pattern 40 has a thickness of at least about an order of magnitude less than that of each of the lower metal lines 30 and 31. Thus, it is difficult to precisely form a thin film resistor by this process.
In the semiconductor device of FIG. 2, a thin film resistor head contact pattern 51 and a thin film resistor head pattern 52 are formed on a thin film resistor pattern 40, and the thin film resistor head pattern 52 and a via 71 are connected to each other. The semiconductor device of FIG. 2 has a relatively complicated manufacturing process because four patterning and etching processes are required to form the thin film resistor 40, the thin film resistor head contact pattern 51, thin film resistor head pattern 52, and via 71. Also, to prevent the thin film resistor pattern 40 from being damaged in the etching process, both dry and wet etching processes (oxide etch, HF-based, etc.) are performed. The HF-based process is used in a front end of the line (FEOL) process, but is not used in a back end of the line (BEOL) process. To prevent metallic contamination, equipment designated for patterning the thin film resistor is required.
Also, stress generated by a thermal expansion difference between the thin film resistor head pattern 52 and the thin film resistor pattern 40 may be increased as the thin film resistor head pattern 52 is increased in size. This may cause non-uniform resistance of the thin film resistor head pattern 52 and increase resistance dispersion.